Heater Tube Interference Fit for Electronic Thermostat
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Solution Overview
Problem
The manufacturing process of electronic thermostats is complex and costly due to the requirement of a fastener for coupling the heater to the wax case, leading to increased components, assembly operations, and potential wax leakage issues from loosening screw joints under vehicle vibration.
Innovation Solution
A heater design that eliminates the need for a fastener by directly inserting a hollow tube into a wax case through interference fitting, reducing the number of components and assembly steps, while ensuring sufficient insulation and preventing foreign matter adhesion through insulated lead wires and a heating coil configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fastener is used to couple the heater to the wax case, then the heater can be securely mounted, but the number of components increases and assembly complexity increases
Solution Approach 1:
The tube serving as the heater housing is merged with the mounting function by directly inserting it into the wax case without requiring a separate fastener. This combines the heater housing and mounting structure into a single integrated component, eliminating the fastener and reducing overall device complexity.
Solution Approach 2:
The fastener component is extracted/removed from the assembly by using an interference fit between the tube and wax case. This eliminates the need for the separate fastening component while maintaining secure mounting through the direct fit between the tube outer surface and wax case inner surface.
2Reliability
If a fastener is used to couple the heater to the wax case, then the heater can be securely mounted, but assembly operations increase
Solution Approach 1:
The mounting function is merged into the tube-wax case interface itself, eliminating the need for separate fastening operations. The interference fit between the tube and wax case provides both structural support and mounting security in a single integrated feature, reducing assembly steps.
Solution Approach 2:
The fastener and its associated assembly operations are extracted from the manufacturing process. By using direct interference fitting, the assembly process is simplified to only require inserting the tube into the wax case, eliminating threading, fastening, and tightening operations.
3Reliability
If a fastener with screw joint is used, then the heater can be mounted, but wax leakage may occur due to loosening under vibration
Solution Approach 1:
The screw joint and fastener are extracted from the design, eliminating the source of vibration-induced loosening. The direct interference fit between the tube and wax case creates a rigid, vibration-resistant connection that prevents wax leakage without relying on threaded fasteners that can loosen under vibrational stress.
Solution Approach 2:
Instead of using a fastener that relies on friction and threading to prevent loosening, the design inverts the approach by using a direct interference fit where the tube itself becomes the structural element that resists vibration. The fit is designed to be so tight that vibration cannot cause loosening, reversing the conventional fastening paradigm.
4Reliability
If a fastener is used to couple the heater to the wax case, then mounting is achieved, but manufacturing costs increase
Solution Approach 1:
The tube is designed to serve dual functions: as the heater housing and as the mounting structure. This merging eliminates the need for separate fasteners and reduces the total component count, leading to lower material costs, simplified manufacturing processes, and reduced assembly requirements.
Solution Approach 2:
The fastener component and its associated manufacturing processes are extracted from the design. This eliminates the cost of purchasing, storing, and assembling separate fastening components, reducing overall manufacturing complexity and cost while maintaining secure mounting through the integrated tube-wax case interface.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design simplifies the manufacturing process, enhances clamping force, improves operational reliability, and reduces manufacturing costs by eliminating the need for fasteners and insulators, while preventing wax leakage and electrolysis-related malfunctions.
Implementation Method 1
a coil 113 connected to each of the lead wires 111 is wound around an outer circumferential surface of the bobbin 110... the coil 113 is connected at one end thereof to one of the lead wire 111 and connected at the other end thereof to the other lead wire 111... electric current is delivered to the coil 113 via the lead wires 111 and flows through the coil 113, thereby allowing the coil 113 to generate heat
Implementation Method 2
The tube 120 is inserted into the wax W at the closed end thereof, increases temperature of the wax W using heat generated by the coil 113
Implementation Method 3
The tube 120 is filled with the insulation materials 130... the insulation materials 130 maintain insulation between the tube 120 and the coil 113
Implementation Method 4
a cartridge heater 100 which generates heat upon application of electric power, causing wax to expand... the wax case 9 has a wax receiving space filled with the wax W and is formed at an upper portion thereof with a securing portion 15 on which the cartridge heater is mounted... the cartridge heater 100... generates heat upon application of electric power, thereby selectively applying heat to the wax W
Data Source
AI summary
The present invention is aimed at providing an improved heater for electronic thermostats which can increase clamping force between a wax case and the heater while allowing reduction in the number of components and cost reduction, thereby improving productivity and reducing manufacturing costs in manufacture of an electronic thermostat, while improving durability and operational reliability of an electronic thermostat. The present invention provides a heater for electronic thermostats including: a hollow tube open at one end thereof and closed at the other end thereof; a heating member disposed inside the tube and generating heat by electrical resistance; and lead wires supplying electric power to the heating member, wherein the tube is directly inserted into a fastening hole of a wax case through interference fitting such that the heater is mounted on the wax case.